Thx Si and Helmut #1, got it. so an elaborate truck so to speak since they have some type of body built onto them to lash the logs to.

Helmut #1, yes I apologize if I wasted time but I probably would not have uncovered that Seattle Car and Foundry catalog! Yes, did a google search and no catalog, lots of logging disconnects for the IT industry though.

Just imagine a small flat car with 4 wheels and a swiveling (or not) log bunk on top. Disconnects had couplers at both ends (most used link & pin couplers) so when empty a train of the little cars could be hauled to the cutting area. In later years, disconnects could be used under other cars-water cars, bunk cars, work cars, just about anything. Many times, the disconnects would be coupled together with "roosters" or long poles between them, especially when loaded. That made them a bit "safer". If you are interested in such things, there must be hundreds of books and magazine articles about logging and photos of various disconnected trucks. Loggers quit using them when the newer types of log cars became available, like skeleton and flat car type cars.
Wow...too much history, I could go on however.

Woodie,
nope - interesting actually. The thing about model railroading to me is realizing the actual human innovation and perseverance that went into these machines and operations at that time period in our history. It is absolutely amazing.

I run an engineering group and we have some pretty good tools at our disposal: Solidworks for drawings, of course electronic so revisions are easy to make, a PLM (Product Lifecycle Management) tool for tracking revisions, electronic rulers (micrometer) with digital readouts, pre-made electonic drawings of components we use, etc., etc. And we still have issues designing things. None of that stuff was available then of course. Just amazing.